Dihydroguaiazulenide Complexes and Catalysts of Group 8-12 Transition Metals: Ligands from Renewable Feedstock Replace, even Outmatch Petrochemical Based Cyclopentadienyl Chemistry.

We present an in-depth study of the sterically demanding Cp-synthon (8-H-GuaH)Li isolated from natural product guaiazulene (Gua) as a ligand transfer reagent towards late transition metal complex precursors. The synthesis and full characterization of selected, essentially unexplored homo- and heteroleptic 8-H-guaiazulenide complexes of iron, ruthenium, cobalt, rhodium, platinum, copper and zinc are discussed in detail. In order to demonstrate their potential in catalytic applications, [(GuaH)PtMe3 ] was selected. The latter proved an even higher catalytic activity in light induced olefin hydrosilylation at catalyst loads as low as 5 ppm than classical [CpPtMe3 ] in a typical test reaction of silicone elastomer fabrication. Our results demonstrate that traditional petrochemical based Cp metal chemistry and catalysis can be replaced, sometimes even outmatched by superior catalysts based on cheap building blocks from renewable feedstock.

Halogen-Bridged Methylnaphthyl Palladium Dimers as Versatile Catalyst Precursors in Coupling Reactions.

Halogen-bridged methylnaphthyl (MeNAP) palladium dimers are presented as multipurpose Pd-precursors, ideally suited for catalytic method development and preparative organic synthesis. By simply mixing with phosphine or carbene ligands, they are in situ converted into well-defined monoligated complexes. Their catalytic performance was benchmarked against state-of-the-art systems in challenging Buchwald-Hartwig, Heck, Suzuki and Negishi couplings, and ketone arylations. Their use enabled record-setting activities, beyond those achievable by optimization of the ligand alone. The MeNAP catalysts permit syntheses of tetra-ortho-substituted arenes and bulky anilines in near-quantitative yields at room temperature, allow mono-arylations of small ketones, and enable so far elusive cross-couplings of secondary alkyl boronic acids with aryl chlorides.

Differences in the Performance of Allyl Based Palladium Precatalysts for Suzuki-Miyaura Reactions.

Palladium(II) precatalysts are used extensively to facilitate cross-coupling reactions because they are bench stable and give high activity. As a result, precatalysts such as Buchwald's palladacycles, Organ's PEPPSI species, Nolan's allyl-based complexes, and Yale's 1-tert-butylindenyl containing complexes, are all commercially available. Comparing the performance of the different classes of precatalysts is challenging because they are typically used under different conditions, in part because they are reduced to the active species via different pathways. However, within a particular class of precatalyst, it is easier to compare performance because they activate via similar pathways and are used under the same conditions. Here, we evaluate the activity of different allyl-based precatalysts, such as (η3-allyl)PdCl(L), (η3-crotyl)PdCl(L), (η3-cinnamyl)PdCl(L), and (η3-1-tert-butylindenyl)PdCl(L) in Suzuki-Miyaura reactions. Specifically, we evaluate precatalyst performance as the ancillary ligand (NHC or phosphine), reaction conditions, and substrates are varied. In some cases, we connect relative activity to both the mechanism of activation and the prevalence of the formation of inactive palladium(I) dimers. Additionally, we compare the performance of in situ generated precatalysts with commonly used palladium sources such as tris(dibenzylideneacetone)dipalladium(0) (Pd2dba3), bis(acetonitrile)dichloropalladium(II) (Pd(CH3CN)2Cl2), and palladium acetate. Our results provide information about which precatalyst to use under different conditions.

Dihalogen-bridged NHC-palladium(i) dimers: synthesis, characterisation and applications in cross-coupling reactions.

A di-iodo-bridged PdI dimer bearing an N-heterocyclic carbene ligand was made accessible via the reduction of [(IPr)PdI2]2 in basic methanol solution. The structural features of [(IPr)PdI]2 were explored by single-crystal X-ray analysis. It was found to be a convenient one-component precatalyst with high activity in Suzuki-Miyaura, Buchwald-Hartwig, and Sonogashira reactions.

Dichlorido(3-phenyl-indenyl-idene)bis-(triphenyl-phosphane)ruthenium(II) tetra-hydro-furan disolvate.

The Ru(II) atom in the title compound, [RuCl(2)(C(15)H(10))(C(18)H(15)P)(2)]·2C(4)H(8)O, has a distorted square-pyramidal conformation. The P and Cl atoms are at the base of the pyramid and the Ru-C(indenyl-idene) bond is in the axial position. The two Cl ligands and the two phosphane ligands are in trans positions. The Cl-Ru-Cl and P-Ru-P angles are 157.71 (2) and 166.83 (2)°, respectively. The two independent tetra-hydro-furan (THF) solvent mol-ecules are disordered. One THF mol-ecule was refined using a split-atom model. The second THF mol-ecule was accounted for by using program PLATON/SQUEEZE [Spek (2009 ▶). Acta Cryst. D65, 148-155]. The molecular conformation shows three intramolecular C-H⋯Cl contacts and two C-H⋯π interactions while the crystal packing features an intermolecular C-H⋯Cl contact and two very weak intermolecular C-H⋯π contacts.

Simple synthetic routes to ruthenium-indenylidene olefin metathesis catalysts.

An efficient synthetic protocol involving reactions between the free carbene and [RuCl(2)(PPh(3))(2)(Ind)] followed by addition of pyridine leads to the isolation of olefin metathesis active [RuCl(2)(L)(Py)(Ind)] (L = SIMes and SIPr) complexes. This novel approach circumvents the use of costly tricyclohexylphosphine.

(S)-1-Diphenyl-phosphanyl-2-{(S)-[2-(diphenyl-phosphan-yl)phen-yl]hydroxy-meth-yl}ferrocene.

The absolute configuration of the title compound, [Fe(C(5)H(5))(C(36)H(29)OP(2))], is S(p) at the ferrocene group and S at the asymmetric C atom. Both P atoms have a trigonal-pyramidal conformation. There is a short intra-molecular C-H⋯P contact with an H⋯P distance of 2.56 Å. The hydr-oxy group is involved in an intra-molecular O-H⋯π(phen-yl) inter-action. The crystal packing shows five very weak inter-molecular C-H⋯π contacts, with H⋯Cg distances between 3.26 and 3.39 Š(Cg is the centroid of a phenyl or cyclo-penta-dienyl ring).

(R(p))-1-{(R)-(Dimethyl-amino)[2-(diphenyl-phosphan-yl)phen-yl]methyl}-2-(diphenyl-phosphan-yl)ferrocene chloro-form solvate.

The absolute configuration of the title mol-ecule, [Fe(C(5)H(5))(C(38)H(34)NP(2))]·CHCl(3), is R,R(p). The mol-ecular structure is similar to the structure of the solvent-free compound [Fukuzawa, Yamamoto & Kikuchi (2007 ▶). J. Org. Chem. 72, 1514-1517], but some torsion angles about the P-C(phen-yl) bonds differ by up to 25°. The P atoms and the N atom have a distorted trigonal-pyramidal geometry. The chloro-form solvate group donates a C-H⋯π bond to the central benzene ring and is also involved in six inter-molecular C-H⋯Cl contacts with H⋯Cl distances between 2.96 and 3.13 Å.

Isolation and structural characterization of an optically active intermediate in the oxidative addition of methyl iodide on a rhodium(I) centre.

The optically pure cationic complex (S,S(Rh))-[Rh(eta5-C(5)H(4)CH(2)CH(Ph)PPh(2)-kappaP)(eta2-CH(2)CH(2))(CH(3))][I] is the first example of a key intermediate in the oxidative addition reaction of methyl iodide on a rhodium(I) centre which has been structurally characterized by X-ray diffraction.